Disposable paint strainers are used to filter paint that is to be sprayed from a spray gun, and consist of an impervious structure, usually a low-cost paper board body, with a filter insert. The strainer is usually produced in a conical shape, but this shape is not necessarily required. The conical strainer is typically placed in the opening of a spray gun cup and the paint is poured through the strainer and into the cup to filter the paint. Filtering both mixes the paint for best color match and strains any impurities that may clog a spray gun. If a spray gun clogs during use, the uniformity of the painting is compromised. Consequently, virtually all paint manufacturer's recommend filtering or straining paint that is used in spray guns. Such pre-filtering is recommended for paint used, for example, in auto body repair.
It is important to protect the strainer body and filter from dust, and to avoid touching the strainer filter with the hand or fingers. Dust can dislodge from the filter mesh, drop into the paint cup and can appear as blemishes on the surface of a car or can clog the spray gun. Touching of the filter can transfer body oils or contaminants on the hand to the filter and can result in spotting or “fish eyes” in the paint job, necessitating repainting. Modern paints, especially waterborne paints, are extremely sensitive to contamination by oils and silicone (dimenthylsiloxane), and touching of the filter must be avoided.
Strainers are typically supplied by the manufacturers in cases of 1,000 units. Internal packages within the case of 1000 strainers are typically bags containing 100 or 250 stacked, nested strainers. Strainers are typically supplied packed in a poly bag or overwrap to prevent contamination. Although satisfactory for transportation of the product, this type of packaging is less than desirable for the paint shop. The strainers must be stored in the paint shop, and oftentimes the painter will remove a stack of strainers from the bag and store them on a shelf. Not only does this permit dust to contaminate the strainer, but also the painter might typically remove a strainer in the stack by grasping the tip end, which can transfer both particulate and chemical contaminants from the painter's fingers to the filtering mesh of the strainer. However, even if the strainers are left in the bag, the bag may end up on a shelf or a workbench or even on the floor, where it can be damaged, knocked around or left open. A damaged or open package allows dust to enter the bag, and thus is not desirable. Also, in order to obtain a strainer for use, the painter must reach into the bag and pull out a strainer by hand. If the strainer is dispensed from the bag tip first, the painter is likely to touch and contaminate the outside of the filter.
Over the years, various types of dispensers have been developed to allow for more convenient storage of the strainers. These dispensers have been made from everything from low cost corrugated board to sheet metal. Some conventional dispensers are merely tubes that hold a stack of strainers, and the open ends of the tube do little to avoid exposure of the tip and filter area of the strainer to manual contamination or contamination from dust in the air. In some dispensers, the strainer is typically removed from the top of the dispenser or shipping box, with the painter reaching in to remove a strainer. If the dispenser is mounted at or near chest level, it is difficult to reach into the top of the dispenser, especially when the stack of strainers is almost used and the painter has to reach far down the tube or box to remove the strainer. To overcome this inconvenience s, some strainer dispensers have been made with slots down the front side so that the painter can grab the rim of a strainer and move it up the tube and out of the open top end. However, this slot leaves the carton open to contamination by dust and particles in the atmosphere. Some conventional dispensers are configured to have the strainers dispense from the bottom of the tube, but this has two drawbacks. First, having the strainers dispense from the dispenser bottom leaves the tip and filter of the strainer exposed to the atmosphere, allowing contamination from dust and particulates. Secondly, in order to dispense a strainer from the stack, the strainer is gripped by the tip or filter area of the strainer. This can physically damage the filter or weaken its bond to the paper and/or exposes the filter to contamination from body oils or other chemicals on the hands and fingers.